1. Field of the Invention
The present invention relates generally to anchoring apparatus, and more specifically to apparatus able to be selectively engaged with, and disengaged and withdrawn from, a borehole having a generally uniform circular cross-section.
2. Description of the Related Art
Those who participate in the sport of rock climbing on sheer rock faces rely on safety ropes and various other apparatus to protect them against falls, and to support and move their climbing gear along with them as they climb. Traditionally, permanently-emplaced anchoring apparatus such as pitons and rock bolts have been used for transitory attachment of ropes, carabiners, webbing straps and other support apparatus to the rock face. Conventional pitons comprise a rigid spike with a projecting rigid loop; they are simply pounded into a crack in the rock face with a hammer. Rock bolts may be any of a number of types of apparatus which fall into the general class of mechanical mechanisms commonly referred to as "expansion dowels." These are normally adapted to engage a pre-drilled borehole, and generally comprise a cylindrical, threaded or nonthreaded dowel body, and a distal expansion member adapted to spread radially in response to axial movement of the dowel body. The axial movement may be accomplished by torque as with a wrench, or by axially-directed force as with a hammer.
Pitons have fallen into disfavor because they project dangerously from the rock face; they rust, and can break off and leave more dangerous, sharp remnants; and, they stain and deface the natural rock face. Further, they are quite heavy when enough are carried to complete a substantial climb; they are difficult to recover once emplaced, thus being costly; and, they are dangerous for later climbers to rely upon, not knowing the age of the piton or the experience of the climber who placed it. Yet further, pitons cannot be used in all rock; some rock faces are highly erodible, or have few cracks or fissures for emplacement.
Rock bolts pose many of the same problems as pitons, although many styles of rock bolt are, theoretically, removable. Still, removal of a rock bolt requires unscrewing, prying, and often a significant amount of energy and one or more extra tools for the operation. Thus, rock bolts are generally undesirable, as well.
The sport of rock climbing is currently evolving due to pressure from the public to improve the aesthetics of rock faces used for recreational rock climbing. This is causing park lands management officials and others to order removal of, or at least to prohibit further placement of, such "fixed anchors" as pitons and rock bolts. Thus, even though fixed anchors are undesirable in many respects, climbers who continue to prefer to rely upon them can no longer find them in certain areas.
Simultaneously, over the past ten to fifteen years, or so, climbers have ventured away from climbing routes and sites where fixed anchors are already emplaced. This spurred development of various instantly-emplaceable and removable "chocks" and wedges for lodging in natural cracks and crevices in rock faces. The simplest of these are single-piece, wedge-shaped structures of various sizes, with variously-angled faces, having no moving parts. All have in common a secure, projecting loop to which a carabiner, rope or webbing strap may be secured. This loop is normally constructed of coated, flexible cable, and normally projects from the narrower or thinner end of the wedge-shaped body of the chock. Use is effected by simply forcing the chock into a crack and setting it in place by pulling on its projecting loop in the direction in which the chock will bear weight. However, simple, one-piece chocks have several drawbacks. One is that a great number of different shapes and sizes of chock are needed for different climbs. And, although theoretically removable, once a chock is set in a crack and has been used to bear weight, it is often very difficult to remove and retrieve for later use. Thus, a fair expense may mount in the course of a climb, simply from the loss of chocks which are too difficult to remove. Later climbers rely on such chocks left behind only at great risk, because their age and stability of placement are often difficult to discern. Such abandoned chocks stay in place and degrade, sometimes leaving dangerous, projecting, frayed cable ends. U.S. Pat. No. 4,442,607 issued to Vallance in 1983 shows such a one-piece chock. Others are shown in U.S. Pat. No. 4,082,241 issued to Burkey in 1978, and U.S. Pat. No. 3,957,237 issued to Campbell in 1976.
Multi-piece chocks of various types have been developed to remedy some of the problems encountered in the use of single-piece chocks. Examples of these are shown in U.S. Pat. No. 3,903,785 issued to Pepper, Jr. in 1975; U.S. Pat. No. 4,572,464 issued to Phillips in 1986; and, U.S. Pat. No. 4,715,568 issued to Best in 1987. These devices generally include wedge-shaped subcomponents which are slidingly engaged with one another in a way which causes their combined effective width to increase as force is applied to a cable loop or lanyard in a direction away from the chock. Each such device is able to be used in a wider range of crack sizes than a single-piece chock, thus offering climbers greater weight-carrying economy. And, these are somewhat easier to remove from cracks than single-piece chocks because their machined, abutting faces slide easily over one another, and thus decrease the chock's effective width, in response to force directed opposite to the direction in which weight is borne. Nevertheless, a fair collection of sizes still needs to be carried and, when stuck, they tend to rust, rot and fray like any other chock.
Yet another class of climbing aids, commonly known as "Friends" (U.S. Pat. No. 4,184,657 issued to Jardine in 1980), includes devices having a central support bar and a cross-spindle, with two pairs of oppositely-rotating, gear-toothed cams residing on the spindle. Coil springs on the spindle bias the cams outward, and a pull-bar transverse to the central support and connected to the cams with cables is operable to retract the cams inward toward the central support. In use, such device is inserted in a crack with its cams retracted. When its cams are released, they abut opposing walls of the crack with the cross-spindle in an over-center position. Although "Friends" provide many advantages in certain situations, they have significant drawbacks, as well. These include mechanical complexity, considerable expense, the tendency to "walk" into cracks and become irretrievable.
In light of the mechanical drawbacks and the aesthetic and safety problems caused by the aforedescribed devices, it appears worthwhile to seek a new approach to rock climbing which provides maximum safety against disengagement from the rock; minimizes the amount of gear needed to be carried; minimizes gear loss from irretrievable emplacements; preserves the aesthetics of the rock face; and, utilizes existing alterations to the rock face to the best advantage.